This is thus in particular an invention for Ethernet switches in networks. Furthermore, the invention relates in particular to switches in networks with special environmental conditions. However, the invention does not need to be limited to the use with switches, but it is preferably applicable here. The use of the invention with switches is therefore dealt with below, although it can be used in general with the electronic devices cited above that are connected to a network with at least two network accesses (data ports).
The prior-art protocols used today in the field of Ethernet networks render possible a media redundancy, although the technology on which the network transmission is based, the Ethernet, due to the broadcast characteristics (broadcast topology), is not normally able to work with network circuits (ring topology).
RSTP and MRP protocols are known. RSTP is specified in “IEEE 802.1D-2004:802.1D IEEE Standard for local and metropolitan area networks,” MRP is specified in “Draft IEC 62439-2 Industrial Communications Networks High Availability Automation Networks; Part 2: Media Redundancy Protocol (MRP),” the general mechanism for operating a ring-redundancy protocol on an Ethernet basis is known from WO99/046908 (Local Network, in particular Ethernet network, with redundancy characteristics and redundancy manager) [U.S. Pat. No. 6,430,151].
The MRP protocol is used below by way of example for Ethernet ring-redundancy protocols. The methods are likewise valid for other ring-redundancy protocols, such as, for example, the Fast HiPER ring from Hirschmann or the like.
The RSTP protocol breaks loops in the network topology by administratively blocking individual connection points (for example network ports at which network devices are connected) between the network devices (also referred to as network infrastructure devices, such as, for example, Ethernet switches, routers and the like) and breaking the loop topology into a tree with the highest prioritized network device as a root (root bridge).
In the supported network topologies (in contrast to RSTP) the MRP protocol is limited to a pure ring structure and therefore, in contrast to RSTP, can operate with a method optimized with respect to the determinism of the reconfiguration time.
Both protocols have in common that they suppress the exchange of network traffic via certain ports (also referred to as data ports) of individual network devices with the exception of network traffic for controlling/monitoring the media redundancy in order to avoid an endless recirculation of network traffic, so called loops and/or broadcast storms, in physical loops.
However, to this end a protocol needs exclusive access to resources of a network infrastructure device, namely the network port administration thereof in order to be able to activate and deactivate these ports for normal network traffic as needed.
However, there are no interfaces between the two protocols, which is why both protocols can operate only completely independently of one another. It has not been hitherto ensured that both protocols cooperate without any problems with a common operation of both protocols in a common network. For MRP it is compulsorily required that RSTP must be switched off at the network ports at which MRP is operating in order to avoid problems. It has hitherto been impossible for one and the same RSTP network to be connected at more than one switch in the MRP ring.
Due to this restriction, in the event of an incorrect cabling, loops can occur as shown in FIG. 1. The RSTP connection present in addition to the “ring” structure between the two infrastructure devices RS and RM represented symbolically is not blocked by the RSTP and the loop is not broken, since the protocol cannot detect the loop because it is not activated at the ports at which the MRP ring protocol is operating.
Furthermore, there is the danger of ports being administratively blocked by a redundancy protocol, while other protocols want to switch via this port.
FIG. 2 shows the RSTP root bridge with two switches connected in the ring. The path costs from the RS and RM switches directly to the root bridge are smaller than any other connection to the root bridge. The RSTP thus breaks the loop that has formed by blocking the connection between RS and RM. However, the ring-redundancy protocol configured inside the ring has, independently of this, already automatically blocked another ring port in order to break the loop that the ring represents.